Android系统启动-SystemServer下篇-1

frameworks/base/services/java/com/android/server/
  - SystemServer.java

frameworks/base/services/core/java/com/android/server/
  - SystemServiceManager.java
  - ServiceThread.java
  - am/ActivityManagerService.java

frameworks/base/core/java/android/app/
  - ActivityThread.java
  - LoadedApk.java
  - ContextImpl.java

SystemServer.main
    SystemServer.run
        createSystemContext
        startBootstrapServices();
        startCoreServices();
        startOtherServices();
        Looper.loop();

public final class SystemServer {
    ...
    public static void main(String[] args) {
        //先初始化SystemServer对象，再调用对象的run()方法，【见小节1.2】
        new SystemServer().run();
    }
}

private void run() {
    //当系统时间比1970年更早，就设置当前系统时间为1970年
    if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
        SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
    }

    //变更虚拟机的库文件，对于Android 6.0默认采用的是libart.so
    SystemProperties.set("persist.sys.dalvik.vm.lib.2", VMRuntime.getRuntime().vmLibrary());

    if (SamplingProfilerIntegration.isEnabled()) {
        ...
    }

    //清除vm内存增长上限，由于启动过程需要较多的虚拟机内存空间
    VMRuntime.getRuntime().clearGrowthLimit();

    //设置内存的可能有效使用率为0.8
    VMRuntime.getRuntime().setTargetHeapUtilization(0.8f);
    // 针对部分设备依赖于运行时就产生指纹信息，因此需要在开机完成前已经定义
    Build.ensureFingerprintProperty();

    //访问环境变量前，需要明确地指定用户
    Environment.setUserRequired(true);

    //确保当前系统进程的binder调用，总是运行在前台优先级(foreground priority)
    BinderInternal.disableBackgroundScheduling(true);
    android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_FOREGROUND);
    android.os.Process.setCanSelfBackground(false);

    // 主线程looper就在当前线程运行
    Looper.prepareMainLooper();

    //加载android_servers.so库，该库包含的源码在frameworks/base/services/目录下
    System.loadLibrary("android_servers");

    //检测上次关机过程是否失败，该方法可能不会返回[见小节1.2.1]
    performPendingShutdown();

    //初始化系统上下文 【见小节1.3】
    createSystemContext();

    //创建系统服务管理
    mSystemServiceManager = new SystemServiceManager(mSystemContext);
    //将mSystemServiceManager添加到本地服务的成员sLocalServiceObjects
    LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);


    //启动各种系统服务
    try {
        startBootstrapServices(); // 启动引导服务【见小节1.4】
        startCoreServices();      // 启动核心服务【见小节1.5】
        startOtherServices();     // 启动其他服务【见小节1.6】
    } catch (Throwable ex) {
        Slog.e("System", "************ Failure starting system services", ex);
        throw ex;
    }

    //用于debug版本，将log事件不断循环地输出到dropbox（用于分析）
    if (StrictMode.conditionallyEnableDebugLogging()) {
        Slog.i(TAG, "Enabled StrictMode for system server main thread.");
    }
    //一直循环执行
    Looper.loop();
    throw new RuntimeException("Main thread loop unexpectedly exited");
}

private void performPendingShutdown() {
    final String shutdownAction = SystemProperties.get(ShutdownThread.SHUTDOWN_ACTION_PROPERTY, "");
    if (shutdownAction != null && shutdownAction.length() > 0) {
        boolean reboot = (shutdownAction.charAt(0) == '1');

        final String reason;
        if (shutdownAction.length() > 1) {
            reason = shutdownAction.substring(1, shutdownAction.length());
        } else {
            reason = null;
        }
        // 当"sys.shutdown.requested"值不为空,则会重启或者关机
        ShutdownThread.rebootOrShutdown(null, reboot, reason);
    }
}

private void createSystemContext() {
    //创建system_server进程的上下文信息
    ActivityThread activityThread = ActivityThread.systemMain();
    mSystemContext = activityThread.getSystemContext();
    //设置主题
    mSystemContext.setTheme(android.R.style.Theme_DeviceDefault_Light_DarkActionBar);
}

private void startBootstrapServices() {
    //阻塞等待与installd建立socket通道
    Installer installer = mSystemServiceManager.startService(Installer.class);

    //启动服务ActivityManagerService
    mActivityManagerService = mSystemServiceManager.startService(ActivityManagerService.Lifecycle.class).getService();
    mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
    mActivityManagerService.setInstaller(installer);

    //启动服务PowerManagerService
    mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);

    //初始化power management
    mActivityManagerService.initPowerManagement();

    //启动服务LightsService
    mSystemServiceManager.startService(LightsService.class);

    //启动服务DisplayManagerService
    mDisplayManagerService = mSystemServiceManager.startService(DisplayManagerService.class);

    //Phase100: 在初始化package manager之前，需要默认的显示.
    mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);

    //当设备正在加密时，仅运行核心
    String cryptState = SystemProperties.get("vold.decrypt");
    if (ENCRYPTING_STATE.equals(cryptState)) {
        mOnlyCore = true;
    } else if (ENCRYPTED_STATE.equals(cryptState)) {
        mOnlyCore = true;
    }

    //启动服务PackageManagerService
    mPackageManagerService = PackageManagerService.main(mSystemContext, installer, 
        mFactoryTestMode != FactoryTest.FACTORY_TEST_OFF, mOnlyCore);
    mFirstBoot = mPackageManagerService.isFirstBoot();
    mPackageManager = mSystemContext.getPackageManager();

    //启动服务UserManagerService，新建目录/data/user/
    ServiceManager.addService(Context.USER_SERVICE, UserManagerService.getInstance());

    AttributeCache.init(mSystemContext);

    //设置AMS
    mActivityManagerService.setSystemProcess();

    //启动传感器服务
    startSensorService();
}

private void startCoreServices() {
    //启动服务BatteryService，用于统计电池电量，需要LightService.
    mSystemServiceManager.startService(BatteryService.class);

    //启动服务UsageStatsService，用于统计应用使用情况
    mSystemServiceManager.startService(UsageStatsService.class);
    mActivityManagerService.setUsageStatsManager(LocalServices.getService(UsageStatsManagerInternal.class));

    mPackageManagerService.getUsageStatsIfNoPackageUsageInfo();

    //启动服务WebViewUpdateService
    mSystemServiceManager.startService(WebViewUpdateService.class);
}

private void startOtherServices() {
    ...
    SystemConfig.getInstance();
    mContentResolver = context.getContentResolver(); //resolver
    ...
    mActivityManagerService.installSystemProviders(); //provider
    mSystemServiceManager.startService(AlarmManagerService.class); //alarm
    // watchdog
    watchdog.init(context, mActivityManagerService); 
    inputManager = new InputManagerService(context); // input
    wm = WindowManagerService.main(...); // window
    inputManager.start();  //启动input
    mDisplayManagerService.windowManagerAndInputReady();
    ...
    mSystemServiceManager.startService(MOUNT_SERVICE_CLASS); //mount
    mPackageManagerService.performBootDexOpt();  // dexopt操作
    ActivityManagerNative.getDefault().showBootMessage(...); //显示启动界面
    ...
    statusBar = new StatusBarManagerService(context, wm); //statusBar
    //dropbox
    ServiceManager.addService(Context.DROPBOX_SERVICE,
                new DropBoxManagerService(context, new File("/data/system/dropbox")));
     mSystemServiceManager.startService(JobSchedulerService.class); //JobScheduler
     lockSettings.systemReady(); //lockSettings

    //phase480 和phase500
    mSystemServiceManager.startBootPhase(SystemService.PHASE_LOCK_SETTINGS_READY);
    mSystemServiceManager.startBootPhase(SystemService.PHASE_SYSTEM_SERVICES_READY);
    ...
    // 准备好window, power, package, display服务
    wm.systemReady();
    mPowerManagerService.systemReady(...);
    mPackageManagerService.systemReady();
    mDisplayManagerService.systemReady(...);
    
    //重头戏[见小节2.1]
    mActivityManagerService.systemReady(new Runnable() {
        public void run() {
          ...
        }
    });
}

public final class SystemServer {

    private void startBootstrapServices() {
      ...
      //phase100
      mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);
      ...
    }

    private void startCoreServices() {
      ...
    }

    private void startOtherServices() {
      ...
      //phase480 && 500
      mSystemServiceManager.startBootPhase(SystemService.PHASE_LOCK_SETTINGS_READY);
      mSystemServiceManager.startBootPhase(SystemService.PHASE_SYSTEM_SERVICES_READY);
      
      ...
      mActivityManagerService.systemReady(new Runnable() {
         public void run() {
             //phase550
             mSystemServiceManager.startBootPhase(
                     SystemService.PHASE_ACTIVITY_MANAGER_READY);
             ...
             //phase600
             mSystemServiceManager.startBootPhase(
                     SystemService.PHASE_THIRD_PARTY_APPS_CAN_START);
          }
      }
    }
}

ActivityManagerService
PowerManagerService
LightsService
DisplayManagerService

onBootPhase(100)
    DisplayManagerService
//然后创建大量服务下面列举部分:
    PackageManagerService
    WindowManagerService
    InputManagerService
    NetworkManagerService
    DropBoxManagerService
    FingerprintService
    LauncherAppsService
    …

onBootPhase(480)
    DevicePolicyManagerService

onBootPhase(500)
    AlarmManagerService
    JobSchedulerService
    NotificationManagerService
    BackupManagerService
    UsageStatsService
    DeviceIdleController
    TrustManagerService
    UiModeManagerService

    BluetoothService
    BluetoothManagerService
    EthernetService
    WifiP2pService
    WifiScanningService
    WifiService
    RttService

WindowManagerService.systemReady():
PowerManagerService.systemReady():
PackageManagerService.systemReady():
DisplayManagerService.systemReady():

onBootPhase(550)
    MountService
    TelecomLoaderService
    UsbService
    WebViewUpdateService
    DockObserver
    BatteryService

mActivityManagerService.startObservingNativeCrashes();
WebViewFactory.prepareWebViewInSystemServer();
startSystemUi(context);

networkScoreF.systemReady();
networkManagementF.systemReady();
networkStatsF.systemReady();
networkPolicyF.systemReady();
connectivityF.systemReady();
audioServiceF.systemReady();
Watchdog.getInstance().start();

onBootPhase(600)
    JobSchedulerService
    NotificationManagerService
    BackupManagerService
    AppWidgetService
    GestureLauncherService
    DreamManagerService
    TrustManagerService
    VoiceInteractionManagerService

WallpaperManagerService
InputMethodManagerService
LocationManagerService
CountryDetectorService
NetworkTimeUpdateService
CommonTimeManagementService
TextServicesManagerService
AssetAtlasService
InputManagerService
TelephonyRegistry
MediaRouterService
MmsServiceBroker

onStart() --> publishBinderServices() //SensorService.java
onBootPhase(int phase) //SensorService.java 服务内只在指定启动阶段进行响应
startOtherServices() --> wm.systemReady() //SystemServer.java

/ # getprop | grep persist.sys.dalvik.vm.lib.2
[persist.sys.dalvik.vm.lib.2]: [libart.so]